The relief of our planet is amazingly diverse. This article will focus on the dunes. How and where are they formed? And what are these picturesque natural formations?
Aeolian relief. Dunes are ...
Geography studies not only countries and cities. The scope of interest of this science also includes relief - the totality of all the irregularities on the surface of planet Earth. Geomorphology (a special section of geography) studies its basic forms, genesis, and also distribution.
The relief is different. Almost all forces and phenomena observed in our world are involved in the process of its formation. So, some landforms arise under the influence of the Earth’s internal energy, while others are formed by permanent or temporary watercourses. But the dunes are nothing more than a classic wind product.
Dune is one of the forms of the so-called aeolian relief. This term comes from the name of the ancient Greek character, the demigod Aeolus. According to myths, he is the main lord of the winds.
Aeolian processes are accompanied by the transfer of small sandy, clayey or dusty particles to certain distances, their accumulation and distribution on the earth's surface. The most suitable conditions for these processes are in the desert and semi-desert zones, where the material of sediments is not fixed by the root systems of plants.
The main forms of aeolian relief are dunes and dunes. These are sandy natural formations that differ from each other in shape, size, and also the place of their formation. Dunes are formed exclusively in deserts, have a crescent shape and reach a height of 60-70 meters. In turn, the dunes are a smaller relief that is widely found along the shores of lakes, seas and large rivers. We will discuss them in more detail below.
Dunes - what is it? Formation and main types of dunes
If there are shrubs, boulders, remains of walls on the seashore or any large reservoir, this is an excellent prerequisite for the formation of the described relief form. What are dunes? In simple words, these are sand hills created by the wind. Tiny grains of sand accumulate over time near some kind of obstacle. So dunes are formed, the shape of which in plan depends on the wind rose of a particular area.
The heights of the dunes, as a rule, range from 20 to 40 meters. In some parts of the planet there are real sand giants up to 100-150 meters (for example, on the shores of the Bay of Biscay). Their windward slope is usually gentle (about 10-15 degrees), and the leeward is about twice as steeper. Single dunes are quite rare. Most often they form elongated chains of hills of sand.
Depending on the shape of the dune, they are divided into three types:
- horseshoe-shaped (formed when the wind blows in the same direction year round);
- transverse (formed in places with a lot of sand);
- stellar (the most picturesque dunes formed in places where the wind often changes direction).
Dune movement
These amazing natural formations also move! This happens, again, under the influence of the wind. He rolls grains of sand from one slope to another, forcing the dunes to change their position in space. Their speed is low - about 20-30 meters per year.
It is important to note that the movement of the dunes is a real problem. After all, wandering sand hills destroy crops in the fields, roads, pastures and even entire villages fall asleep. People are trying to deal with this phenomenon by fixing sand. To do this, grass, trees and shrubs are planted on the windward slopes of dunes and dunes. Plants keep grains of sand from further “travels” with their root systems.
The most famous dunes of the planet
France, Namibia, Russia, Wales and Australia - what unites all these countries? That's right - the dunes! Each of them has its own “marvel of sand”. Let's talk about them in order.
Dune Pyla (France) is the highest in Europe. It is located on the shores of the Arcachon Bay of the Atlantic and has a height of 130 meters. This place is very popular among tourists. It is interesting that every year the Saw moves several meters deep into the centuries-old pine forest.
"Big Daddy" (Namibia) - the highest dune of the Namib desert (304 meters). The conquest of this orange-red sandy mountain is a must for any tourist who comes here.
Elevation Efa (Russia) is an interesting natural site located on the Curonian Spit, in the Kaliningrad Region. The maximum height of this dune is 64 meters. A special hiking trail leads to its top.
Dune Inislas (Wales) is one of the most picturesque places in this part of Britain. Moreover, Inislas does not look lifeless at all, it is almost completely covered with beautiful herbs and wildflowers. In addition, the dune is unusually mobile and constantly changes its shape.
Mount Tempest (Australia) is considered the second highest dune in the world (285 meters). It is located in the north-east of the country, near the city of Brisbane. The dune attracts the attention of not only travelers, but also professional photographers, because from its top a wonderful view of the Australian coast opens.
Conclusion
So, the dunes are a landform of aeolian origin. That is, its main "builder" and "sculptor" is the wind. Dunes are formed on the shores of large reservoirs, are small in size and mobility.